Method and apparatus for transmission scheduling in wireless sensor network

Abstract

In a sensor network including a sink node and a plurality of sensor nodes, the sink node receives a routing message including routing information from the sensor nodes, analyzes a structure of the sensor network based on routing information, and calculates a transmission schedule of each sensor node based on the analyzed network structure. Schedule information according to the calculated transmission schedule includes a wakeup time of the sensor node, a time interval that is consumed for packet transmission, and a standby time for preventing a packet collision based on the time interval.

What is claimed is: 
     
         1 . A method in which a sink node performs transmission scheduling in a sensor network comprising the sink node and a plurality of sensor nodes, the method comprising:
 receiving, by the sink node, a routing message comprising routing information from the sensor nodes;   analyzing, by the sink node, a structure of the sensor network based on the routing information and calculating a transmission schedule of each sensor node based on the analyzed network structure; and   transmitting a schedule message comprising schedule information according to the calculated transmission schedule to the sensor nodes,   wherein the schedule information comprises a wakeup time of the sensor node, a time interval that is consumed for transmitting a packet, and a standby time for preventing a packet collision based on the time interval.   
     
     
         2 . The method of  claim 1 , wherein the schedule information further comprises a hop number and a node number from the sensor node to the sink node. 
     
     
         3 . The method of  claim 1 , wherein the standby time is xγ′, where γ′ represents a time interval and x satisfies a condition Of 3≦x≦X. 
     
     
         4 . The method of  claim 1 , wherein the calculating of a transmission schedule comprises,
 when the sensor network comprises a plurality of routing path branches based on a junction node:   calculating the node number on a routing path branch basis; and   calculating a transmission schedule on a routing path branch basis according to a priority order based on the node number.   
     
     
         5 . The method of  claim 4 , further comprising calculating a transmission schedule of sensor nodes that are included in each branch in order from a branch having the smallest node number. 
     
     
         6 . The method of  claim 1 , wherein the schedule message is formed based on a pioneer frame (PION frame) structure, and comprises an initial transmission schedule field comprising an initial value of a wakeup time of the sensor node, an interfacing time information field comprising a time interval and a standby time that are consumed for transmitting a packet, and a hop count field representing an end-to-end hop number. 
     
     
         7 . A method in which a sensor node performs transmission scheduling in a sensor network comprising a sink node and a plurality of sensor nodes, the method comprising:
 receiving, by a sensor node, a schedule message comprising schedule information from the sink node; and   determining a wakeup time for transmitting/receiving data based on the schedule information,   wherein the schedule information comprises an initial value of a wakeup time of the sensor node, a time interval that is consumed for transmitting a packet, and a hop number and a node number from the sensor node to the sink node.   
     
     
         8 . The method of  claim 7 , wherein in the determining of a wakeup time,
 the wakeup time is determined as T wakeup ←t 0 +(N−h−l)·γ′, where γ′ is a time interval, N is the node number, t 0  is the initial value, and h is the hop number.   
     
     
         9 . The method of  claim 7 , further comprising:
 waking up, by the sensor node, at the wakeup time and detecting a channel;   determining, when a packet to perform relay transmission exists at the channel, a transmitting time of the relay packet; and   determining a schedule time to receive a next packet.   
     
     
         10 . The method of  claim 9 , wherein the determining of a transmitting time comprises determining the transmitting time based on the determined wakeup time and the time interval, and
 the determining of a schedule time comprises determining the schedule time based on the determined wakeup time and the standby time.   
     
     
         11 . The method of  claim 9 , further comprising, after the waking up at the wakeup time,
 determining, when the sensor node generates a packet to transmit, a transmitting time for transmitting the generated packet,   wherein a transmitting time for transmitting the generated packet is determined based on the standby time.   
     
     
         12 . The method of  claim 7 , wherein a sensor node that is positioned at a terminal of the sensor network first starts data transmission, and adjacent sensor nodes existing within the predetermined hop number from a sensor node that performs data transmission do not perform data transmission when the sensor nodes are disposed in a linear structure in the sensor network. 
     
     
         13 . The method of  claim 7 , wherein data transmission is performed in order of a branch having the smallest node number, and after data transmission of sensor nodes belonging to a random branch is complete, data transmitting of sensor nodes belonging to a branch of a next order is performed, when sensor nodes are disposed while forming at least one branch based on a junction node according to a tree structure in the sensor network. 
     
     
         14 . The method of  claim 7 , further comprising transmitting, by the sensor node, a routing message comprising routing information to the sink node, before receiving of a schedule message,
 wherein the routing information comprises the transmitting hop number to the sink node according to a routing path, an address or identification information of the sensor node, and identification information of an upward node.   
     
     
         15 . A scheduling apparatus that performs transmission scheduling in a sensor network comprising a sink node and a plurality of sensor nodes, the scheduling apparatus comprising:
 a wireless communication unit that performs communication with nodes that are positioned at a periphery;   a transmitting power controller that determines transmitting power of the wireless communication unit based on channel state information that is provided from nodes;   a network analysis unit that analyzes a network structure based on routing information that is received from nodes; and   a schedule calculator that calculates a node number on a routing path branch basis that is acquired based on a network structure and that calculates a transmission schedule in order of a branch having the smallest node number.   
     
     
         16 . The scheduling apparatus of  claim 15 , wherein the schedule calculator generates schedule information comprising a wakeup time of a sensor node, a time interval that is consumed for transmitting a packet, and a standby time for preventing a packet collision based on the time interval and transmits the schedule information to the sensor node through the wireless communication unit. 
     
     
         17 . The scheduling apparatus of  claim 15 , wherein the routing information comprises a transmitting hop number to the sink node according to a routing path, an address or identification information of the sensor node, and identification information of an upward node, and
 the network analysis unit acquires routing path branches that are connected to a junction node based on the routing information.